The invention relates to controlling activation of devices, such as downhole devices found in wellbores.
In a well, various devices may be activated to perform different tasks. Downhole devices may include valves (e.g., flow control valves or safety valves), perforating guns, and other completion components. Different forms of activation mechanisms, including hydraulic, mechanical, or electrical mechanisms, may be used. Mechanical activation typically involves lowering some type of setting or shifting tool to a desired depth to engage the downhole device to apply a force to move an actuator operably coupled to the downhole device. Hydraulic activation typically involves application of hydraulic pressure either through a tubing, a tubing-casing annulus, or a hydraulic control line to an actuator in a downhole device. Electrical activation typically involves communicating electrical power and/or signaling down an electrical cable, such as a wireline, an electrical control line, or other type of electrical line to a downhole actuator, which may include an electronic controller, a motor, or a solenoid actuator.
A solenoid actuator includes an electrical solenoid coil made up of a plurality of helically wound turns of an electrical wire. An armature that is typically constructed of a magnetic responsive material is positioned inside the solenoid. When an electrical current is run through the solenoid coil, a magnetic field is generated to move the armature in a desired direction. The movement of the armature may be used to actuate downhole devices.
Conventional solenoid actuators require relatively high levels of electrical power to perform the desired actuation. Such relatively large power requirements are due in part to the relatively large displacements of actuators to operate a downhole device. Electrical cables may run thousands to tens of thousands of feet to a device in a wellbore. Such long lengths of electrical cables are associated with large resistances in which power loss may be significant. Thus, communication of relatively high electrical currents may require use of heavy cabling as well as high capacity power sources at the well surface. This may increase costs associated with operation of a well.
Other types of actuator mechanisms, such as mechanical or hydraulic mechanisms, may also be associated with drawbacks. Mechanical actuation may require intervention or physical manipulation of downhole equipment, which may be time-consuming and impractical (such as in a subsea well). Communicating hydraulic pressure to certain parts of a well may be difficult, and any leaks in a hydraulic communications path may render a hydraulic actuation mechanism inoperable.
A need thus exists for actuators that are more efficient, reliable, and convenient to use.
In general, according to one embodiment, an apparatus for operating a device includes at least first and second actuators activable by an input energy. An operator member is adapted to be moved in incremental steps by the first actuator and latched in its current position by the activable actuator.
Other embodiments and features will become apparent from the following description, the drawings, and the claims.